1. Field of the Invention
The present invention relates to a process for preparing optical active tryptophans by biochemical asymmetric hydrolysis of DL-tryptophan amides, in which an amidase derived from a microorganism is utilized.
2. Description of the Prior Art
It is well-known in the art that L-tryptophans and D-tryptophans are optically active and have different properties and uses. For instance, L-tryptophan is an important compound as an essential amino acid and is suitable for use in an amino acid infusion solution, an animal food stuff additive, hypnotizing agent and the like. On the other hand, D-tryptophan is useful as, for example, a dentifrice additive and a sweetening agent.
Many organic synthesis methods for preparing tryptophans have been heretofore proposed. However, when the tryptophans are prepared by organic synthesis methods, the products are obtained in the form of mixtures of D-tryptophans and L-tryptophans, i.e. racemic mixtures. Therefore, the effective optical resolution of DL-tryptophans is an extremely important problem to be solved in the art.
Proposed optical resolution methods of DL-tryptophans are only those in which hydantoin or N-acyl derivatives of DL-tryptophans are used as a substrate and in which microorganisms capable of producing hydantoinase or acylase are interacted with the substrate. Thus, the development of the substrate and the microorganisms used in the field of the biochemical optical resolution of DL-tryptophans are extremely limited.